High-redshift radio galaxies: a potential new source of 21-cm fluctuations

ABSTRACT Radio sources are expected to have formed at high redshifts, producing an excess radiation background above the cosmic microwave background (CMB) at low frequencies. Their effect on the redshifted 21-cm signal of neutral hydrogen is usually neglected, as it is assumed that the associated background is small. Recently, an excess radio background has been proposed as a possible explanation for the unusually strong 21-cm signal reported by EDGES. As a result, the implications of a smooth and extremely strong excess radio background on both the sky-averaged 21-cm signal and its fluctuations have been considered. Here, we take into account the inhomogeneity of the radio background created by a population of high-redshift galaxies and show that it adds a new type of 21-cm fluctuations to the well-known contributions of density, velocity, Ly α coupling, heating, and reionization. We find that a population of high-redshift galaxies even with a moderately enhanced radio efficiency (unrelated to the EDGES result) can have a significant effect on the 21-cm power spectrum and global signal. For models that can explain the EDGES data, we show that the 21-cm power spectrum at z ∼ 17 is enhanced by up to two orders of magnitude compared to the CMB-only standard case, with a significantly modified shape and time evolution due to radio fluctuations. These fluctuations are within reach of upcoming radio interferometers. We also find that these models can be significantly constrained by current and future observations of radio sources.

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Shedding light on high-redshift galaxies with the 21cm signal

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001118 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 69-69

Author(s):

Anne Hutter

Keyword(s):

Galaxy Evolution ◽

High Redshift ◽

Neutral Hydrogen ◽

First Stars ◽

High Redshift Galaxies ◽

Redshift Galaxy ◽

First Galaxies ◽

Galaxy Population ◽

The Impact ◽

Redshift Galaxies

AbstractReionization represents an important epoch in the history in the Universe, when the first stars and galaxies gradually ionize the neutral hydrogen in the intergalactic medium (IGM). Understanding the nature of the ionizing sources, the associated ionization of the IGM, and its impact on subsequent structure formation and galaxy evolution by means of radiative feedback effects, represent key outstanding questions in current astrophysics. High-redshift galaxy observations and simulations have significantly extended our knowledge on the nature of high-redshift galaxies. However, essential properties such as the escape fraction of ionizing photons from galaxies into the IGM and their dependency on galactic properties remain essentially unknown, but determine significantly the distribution and time evolution of the ionized regions during reionization. Analyzing this ionization topology by means of the neutral hydrogen sensitive 21cm signal with radio interferometers such as SKA offers a complementary and unique opportunity to determine the nature of these first galaxies. I will show results from a self-consistent semi-numerical model of galaxy evolution and reionization, and discuss the potential of inferring galactic properties with the 21cm signal as well as the impact of reionization on the high-redshift galaxy population and its evolution.

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Results from Searches for High-Redshift Galaxies around Damped Lyα Systems

Symposium - International Astronomical Union ◽

10.1017/s0074180900232506 ◽

1996 ◽

Vol 171 ◽

pp. 291-294

Author(s):

S. J. Warren ◽

P. Møller

Keyword(s):

Narrow Band ◽

Narrow Band Imaging ◽

High Redshift ◽

Neutral Hydrogen ◽

The Other ◽

High Redshift Galaxies ◽

Groups Of Galaxies ◽

Damped Systems ◽

The Universe ◽

Redshift Galaxies

There was not much said at this conference about the damped Lyα absorbers, yet locally and at high redshift nearly all the neutral hydrogen in the Universe lies in the damped systems, so they may have much to tell us about when and how galaxies formed. This talk is concerned with the results of narrow-band imaging searches for Lyα emission from, and around, damped Lyα absorbers. There have been many such searches, but very few detections. Here we concentrate on two groups of galaxies at high redshift, z > 2, found by this technique. One of these is a recent discovery (Francis et al. 1995), and for the other we discuss some new observations (Warren and Møller 1995). A study of these two groups provides some clues to the nature of the damped absorbers at high redshift, and the rôle they play in the formation of galaxies.

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The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stv1414 ◽

2015 ◽

Vol 452 (2) ◽

pp. 2034-2056 ◽

Cited By ~ 90

Author(s):

Alireza Rahmati ◽

Joop Schaye ◽

Richard G. Bower ◽

Robert A. Crain ◽

Michelle Furlong ◽

...

Keyword(s):

High Redshift ◽

Neutral Hydrogen ◽

High Redshift Galaxies ◽

Redshift Galaxies

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TRACING THE EVOLUTION OF HIGH-REDSHIFT GALAXIES USING STELLAR ABUNDANCES

The Astrophysical Journal ◽

10.3847/0004-637x/820/1/71 ◽

2016 ◽

Vol 820 (1) ◽

pp. 71 ◽

Cited By ~ 5

Author(s):

Brian D. Crosby ◽

Brian W. O’Shea ◽

Timothy C. Beers ◽

Jason Tumlinson

Keyword(s):

High Redshift ◽

Stellar Abundances ◽

High Redshift Galaxies ◽

Redshift Galaxies

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Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa527 ◽

2020 ◽

Vol 493 (3) ◽

pp. 4315-4332 ◽

Cited By ~ 14

Author(s):

Xiangcheng Ma ◽

Michael Y Grudić ◽

Eliot Quataert ◽

Philip F Hopkins ◽

Claude-André Faucher-Giguère ◽

...

Keyword(s):

High Pressure ◽

Star Formation ◽

High Redshift ◽

Cluster Formation ◽

Mass Function ◽

Cosmological Simulations ◽

High Redshift Galaxies ◽

Cluster Mass ◽

Formation Efficiency ◽

Redshift Galaxies

ABSTRACT We report the formation of bound star clusters in a sample of high-resolution cosmological zoom-in simulations of z ≥ 5 galaxies from the Feedback In Realistic Environments project. We find that bound clusters preferentially form in high-pressure clouds with gas surface densities over $10^4\, \mathrm{ M}_{\odot }\, {\rm pc}^{-2}$, where the cloud-scale star formation efficiency is near unity and young stars born in these regions are gravitationally bound at birth. These high-pressure clouds are compressed by feedback-driven winds and/or collisions of smaller clouds/gas streams in highly gas-rich, turbulent environments. The newly formed clusters follow a power-law mass function of dN/dM ∼ M−2. The cluster formation efficiency is similar across galaxies with stellar masses of ∼107–$10^{10}\, \mathrm{ M}_{\odot }$ at z ≥ 5. The age spread of cluster stars is typically a few Myr and increases with cluster mass. The metallicity dispersion of cluster members is ∼0.08 dex in $\rm [Z/H]$ and does not depend on cluster mass significantly. Our findings support the scenario that present-day old globular clusters (GCs) were formed during relatively normal star formation in high-redshift galaxies. Simulations with a stricter/looser star formation model form a factor of a few more/fewer bound clusters per stellar mass formed, while the shape of the mass function is unchanged. Simulations with a lower local star formation efficiency form more stars in bound clusters. The simulated clusters are larger than observed GCs due to finite resolution. Our simulations are among the first cosmological simulations that form bound clusters self-consistently in a wide range of high-redshift galaxies.

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New methods for identifying Lyman continuum leakers and reionization-epoch analogues

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2355 ◽

2020 ◽

Vol 498 (1) ◽

pp. 164-180 ◽

Cited By ~ 2

Author(s):

Harley Katz ◽

Dominika Ďurovčíková ◽

Taysun Kimm ◽

Joki Rosdahl ◽

Jeremy Blaizot ◽

...

Keyword(s):

Emission Line ◽

Galaxy Formation ◽

Dwarf Galaxy ◽

High Redshift ◽

Indirect Methods ◽

High Redshift Galaxies ◽

Lyman Continuum ◽

The Universe ◽

Ionization Parameter ◽

Redshift Galaxies

ABSTRACT Identifying low-redshift galaxies that emit Lyman continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly ‘analogues’ of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at z ∼ 3 and z ∼ 0. We find that the simulated galaxies with high LyC escape fractions (fesc) often exhibit high O32 and populate the same regions of the R23–O32 plane as z ∼ 3 LyC leakers. However, we show that viewing angle, metallicity, and ionization parameter can all impact where a galaxy resides on the O32–fesc plane. Based on emission line diagnostics and how they correlate with fesc, lower metallicity LyC leakers at z ∼ 3 appear to be good analogues of reionization-era galaxies. In contrast, local [S ii]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the S ii Baldwin–Phillips–Terlevich (BPT) diagram; however, this diagnostic may still be useful for identifying leakers. We use our simulated galaxies to develop multiple new diagnostics to identify LyC leakers using infrared and nebular emission lines. We show that our model using only [C ii]158 μm and [O iii]88 μm can identify potential leakers from non-leakers from the local Dwarf Galaxy Survey. Finally, we apply this diagnostic to known high-redshift galaxies and find that MACS 1149_JD1 at z = 9.1 is the most likely galaxy to be actively contributing to the reionization of the Universe.

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